Recently, blood component transfusion in which components of blood (whole blood) obtained by blood donation or the like are separated and only the components required by a patient are provided has been conducted in blood transfusion. According to the blood component transfusion, it is possible to alleviate a burden on the patient's circulatory system and other side effects, and effective utilization of the donated blood is achieved.
Blood (whole blood) obtained from blood donation or blood components prepared from the whole blood are separated into a plurality of layers in a blood bag by centrifugation. For example, when residual components (white-cell-poor platelet-poor blood) obtained by removing white blood cells and platelets from whole blood are divided into plasma and red blood cells (concentrated red blood cells) and collected into different bags, the components are first divided into a plasma layer as a supernatant component and a layer of the red blood cells (concentrated red blood cells) as a sedimentary component by centrifugation (a centrifugation step). Thereafter, the plasma is transferred to a plasma bag via a tube connected to the blood bag so as to leave the concentrated red blood cells in the blood bag (a separation transfer step). Next, a red blood cell storage solution housed in a liquid medicine bag transferred into the blood bag via the tube such that the redblood cell storage solution is added to the concentrated red blood cells (an addition step). Incidentally, a centrifuge that performs the above-described centrifugation step and separation transfer step is disclosed, for example, in U.S. Pat. No. 6,910,998.